Whereas the regular pluralization in English involves adding -s or -es, English words derived from a Latin/Greek where the Latin/Greek would pluralize from -on (Greek) or -um (Latin) to -a do not always do so. Usage of -a instead of -s differs between words: sometimes the two are interchangeable (e.g. memorandums/memoranda, polyhedrons/polyhedra), sometimes one is far more common than the other (e.g. neurons over neura, automata over automatons), and sometimes one is completely absent from usage (e.g. bacteria over bacteriums, dendrons over dendra)

Traditionally, if the noun is in definite singular form it should not refer to a male human, if it uses the suffix -a. If it refers to such a person, the suffix should instead be -e, but one should note that this rule is not universally adhered to - in particular dialects of northern Sweden does not recognize the -e suffix at all, but use -a in all instances.

A morpheme used to mark the genitivesingular of a word (such as a noun, adjective or pronoun). It is also the most common morpheme used in creating innumerable compound words, some of which can be very long (e.g., pledadinaselidöp "toy store, toy shop", tanoganilamedin "antibiotic", taglumaladälamedin "anti-depressant", natrinakarbatazüd telik "bicarbonate of soda").